Theatregoers suffering from First World War fatigue may want to pass on Jonathan Lynn’s merely competent historical drama about two mythic figures: Charles de Gaulle and Philippe Pétain. It’s a fascinating subject – de Gaulle had his former mentor tried for treason in 1945 after Pétain led France into Nazi collaboration – but Yes Minister co-creator Lynn, who also directs, seems unsure whether it warrants winking satire or solemn historical re-enactment, settling for a fitfully engaging hybrid.